Device for heating and frothing a liquid, in particular milk

ABSTRACT

An automatic device for heating and frothing a liquid, in particular milk, comprises a container which is provided with an opening for the introduction of the liquid and is associated with a duct for introducing into the liquid pressurised steam for heating the liquid itself and creating turbulence therein, and air, which duct has, in an internal end portion, a set of openings or nozzles distributed along said end portion and is arranged so as to send steam into the liquid according to a predetermined trajectory.

[0001] The present invention concerns a device for heating and frothinga liquid, in particular milk.

[0002] Preferably, the invention is applied in espresso coffee machinesfor bars, for producing frothy hot milk to be used e.g. in preparingcappuccinos, and the following description refers to that preferredapplication.

[0003] It is known that, in order to produce milk froth by means ofespresso coffee machines, the operator utilises a container into whichhe pours a certain quantity of milk; then he introduces steam into themilk by means of a spout while stirring the container, so as to create acertain turbulence in the milk and incorporate the ambient air necessaryto form the froth.

[0004] The characteristics and the quantity of the froth produced dependon the modalities of milk stirring and steam introduction, and thereforeon the sensitivity and the skill of each operator. Thus, suchcharacteristics, and therefore the characteristics of the cappuccino inwhich the frothy milk is used, change from one operator to another andmay be wholly unsatisfactory for the client even if the operator judgesthem optimal.

[0005] Moreover, with the present technique, problems may also arisefrom the hygienic standpoint, due to the presence on the spout tip ofmilk crusts that are produced by successive frothing operations and thatcan remain exposed to air for a certain time, and to the use of milkresiduals that are left in the container after a frothing operation andare heated again, possibly after addition of fresh cold milk.

[0006] Similar problems arise in case of beverages requiring heating,such as chocolate, tea, infusions, punches, etc., the preparation ofwhich is wholly dependent on the operator's skill.

[0007] A partial solution of the above problems is the subject matter ofItalian patent No. 1,236,535. That patent discloses a frothing devicewith a steam spout having a moving part that is manually operated forimmersion into the liquid. The immersion depth is predetermined, so asto ensure a good constancy of the froth characteristics.

[0008] A first aim of the invention is to provide a heating and frothingdevice, which operates in more rational and definite manner, withoutmaking the result depend only on the skill of the person using thedevice.

[0009] Another aim of the invention is to provide an automatic heatingand frothing device, which allows producing a froth with substantiallyconstant characteristics and which does not give rise to the abovementioned hygienic problems.

[0010] The device according to the invention essentially comprises acontainer, acting as a heating and frothing chamber, which is providedwith an opening for the introduction of the liquid to be processed andis associated with a duct for introducing pressurised steam into theliquid, for heating the liquid itself and creating turbulence therein.

[0011] The device according to the invention may be constructed both formanual operation and in an automatic version.

[0012] Advantageously, in the first case the device could be associated,if necessary, with a steam nozzle of a conventional coffee machine,whereas in the second case it will be directly embodied into the coffeemachine.

[0013] The invention will now be described in detail with particularreference to the accompanying drawings, given by way of non limitingexample, in which:

[0014]FIG. 1 as a perspective view of the container of the invention,with a steam-supplying duct applied thereto;

[0015]FIG. 2 is a side view, partly in cross section, of the containershown in FIG. 1 and coupled with a steam-supplying spout;

[0016]FIG. 3 is an axial cross-sectional view of the steam-supplyingduct;

[0017]FIG. 4 is an axial cross-sectional view of the jack connecting thespout and the duct;

[0018]FIG. 5 is an axial cross-sectional view of the member securing theduct to the container bottom;

[0019]FIG. 6 schematically shows the device according to the inventionin the automatic configuration.

[0020] As clearly shown in FIGS. 1 to 5, the device of the inventionessentially comprises an open container 1, of predetermined capacity, tothe bottom of which a duct 3 is removably mounted so that its axis isparallel with the container axis.

[0021] Said duct 3 has a set of openings 5 of predetermined diameters,positions and orientation such that the openings are covered by the milkwhen this is poured in container 1 through its open side.

[0022] In the illustrated embodiment, two downward inclined openings 5with a diameter of the order of 1 mm are provided. Said duct 3 issecured onto the bottom of container 1 by means of a threaded member 7,which is welded onto the bottom of container 1 and in which lower end 9of duct 3 is screwed. Said duct 3 is adapted to receive in sealed mannersteam spout 11 of the coffee machine (not shown). Said coupling betweenduct 3 and spout 11 is achieved through a jack 13, adapted to be fittedinto upper end 15 of duct 3 with the interposition of an O-ring 17, soas to provide a seal between said duct 3 and said spout 11 of the coffeemachine.

[0023] Jack 13 is so shaped as to provide a fastening preventing the twoparts from becoming disconnected and steam from flowing out, what couldbe harmful to the operator.

[0024] Advantageously, jack 13 further provides a mechanical sealallowing use of the device without need of keeping it with the hands, bymerely putting it on a working plane like that usually provided forputting the cups in espresso coffee machines.

[0025] A necessary condition for a good operation of the device is thatthe uppermost opening 5 is to be located some millimeters below thelevel of the milk to be frothed: this obviously entails availability ofa set of containers 1 with a wide range of different capacities, ratherthan of a set of different positions for said openings 5.

[0026] Once the operation is complete, the operator actuates steamdischarge and steam will flow out from said openings 5 thereby stirringthe milk in container 1 to create the turbulence required to heat themilk and to embody the amount of external air required to produce froth.

[0027] After a few seconds of operation, the operator must stop steamdelivery and disconnect duct 3 from spout 11 of the coffee machine,since he has obtained the desired result.

[0028] Referring now to FIG. 6, the automatic device essentiallycomprises a closed container 21 forming a heating and frothing chamber.That chamber has a first inlet duct 22 for introducing milk coming froma vessel 23, a second inlet duct 24 for introducing pressurised steamand a third duct 25 for introducing air. Upper portion 21A of thechamber is mounted in sealed manner on the chamber body and can beremoved to allow washing the chamber itself. The three inlet ductspenetrate into the chamber of container 21 through said upper portion,more particularly through the roof.

[0029] Milk can be transferred from vessel 23 to container 21 by gravityor, preferably, by means of a pump 26, e.g. a peristaltic pump, allowingintroducing dosed amounts of milk.

[0030] Duct 24 extends over the whole height of the chamber of container21 and has a plurality of radial openings or nozzles 27 for steamoutflow in its lower section, for instance three nozzles as shown in thedrawing. Nozzles 27 have a predetermined inclination, preferably adownward inclination, and they are distributed along said lower sectionso that the uppermost nozzle lies near the free surface 20 of the milk,but below that surface.

[0031] Pressurised steam, coming through a duct 28 from a source, notshown, in particular from the steam production unit provided in theespresso coffee machine, is fed to duct 24 through a two-way electricalvalve 29. The second way of that valve allows supplying with steam otherutilisation devices, e.g. the conventional steam spout, through afurther duct 30.

[0032] A valve 31 in turn controls air feed through duct 25.

[0033] The chamber of container 21 further has two outlet ducts 32 and33 for transferring froth and hot milk, respectively, to a cup 34 orother vessel. Duct 32 starts from the side wall of the chamber ofcontainer 21, at an height corresponding with the level of the milk tobe processed, whereas duct 33 starts from the bottom of the chamber ofcontainer 21. Both ducts 32, 33 are equipped with respective valves 35,36.

[0034] The operation cycle of the device is as follows:

[0035] milk is introduced into the chamber of container 21 through duct22, by gravity or by means of pump 26;

[0036] electric valve 29 is operated so as to establish communicationbetween ducts 28 and 24, and steam is introduced into milk throughnozzles 27, thereby heating the milk and inducing turbulence therein;

[0037] air inlet valve 31 is opened, whereby air mixes with theturbulent milk and creates froth;

[0038] after a predetermined time, valve 35 is opened and froth beginsflowing towards cup 34; in the meanwhile the system continues operating,thereby creating further milk froth and heating milk;

[0039] air valve 31 is closed, milk introduction and heating beinghowever continued;

[0040] after a second predetermined time, milk supply is stopped andvalve 36 is opened, thereby discharging hot milk towards cup 34; theformation, during inactivity times, of crusts or impurities that mayalter subsequent operation cycles, is thus prevented.

[0041] The cycle can be started simply by pushing a button on the coffeemachine of which the device is a fitting, and all cycle steps willautomatically follow one another. The flow rates for steam and air andthe heating and frothing times can be set in a calibration phase of themachine.

[0042] One can immediately appreciate that the invention solves theproblems mentioned in the introduction: the operation, as said, iscompletely automatic; the product quality no longer depends on the skilland/or the sensitivity of the individual operator; thanks to the use ofpump 26, it is possible to introduce into the chamber of container 21just the exact milk amount required for a given operation; lastly, theparts contacting the milk (in particular, steam duct 24) no longer areexposed to the ambient atmosphere and thus they do not risk becomingpolluted.

[0043] It is clear that the above description is given only by way ofnon-limiting example and that changes and modifications can be madewithout departing from the scope of the invention.

[0044] Thus, for instance, it is possible to equip the chamber ofcontainer 21 with a probe for detecting and adjusting the temperaturesof the outgoing milk and froth, so as to allow supplying hotter orcolder beverages depending on the client's wishes, or in general,supplying beverages of which the temperature does not depend on thetemperature of the milk in vessel 23.

[0045] Moreover, it is possible to equip the chamber with a furthersteam inlet, which is similar to that consisting of duct 24 and which isfed through an own valve. That further inlet however will have openings27 of which the number, the arrangement and the sizes are such that theydo not give rise to turbulence, and it could be used when supplying merehot milk, without froth, is desired. In such case the control meansshould exclude the air inlet and, of course, the froth outlet, from theoperation cycle.

[0046] Moreover, even if reference has been made to the preparation ofmilk froth and hot milk in espresso coffee machines, the device can beused to froth and/or heat other liquids.

[0047] The possibility of controlling the device according to theinvention allows providing for automatic washing cycles, of desiredintensities and frequencies and automatically timed or manuallyactuated, which ensure an optimum cleanness of the chamber and theducts: this is obtained by simply replacing vessel 23 by a vesselcontaining a suitable commercially available detergent.

1. A device for heating and frothing a liquid, in particular milk,comprising a container (1; 21), acting as a heating and frothingchamber, which is provided with an opening for the introduction of theliquid to be processed into said chamber (1; 21) and with a duct (3; 24)for introducing pressurised steam into the liquid contained in saidcontainer (1; 21), for heating the liquid itself and creating turbulencetherein, said duct having at least one steam outlet opening,characterised in that said duct (3; 24) is fastened to said container(1; 21).
 2. A device according to claim 2 or 3, wherein said duct (3;24) for introducing steam is fastened onto the bottom of the container(1; 21).
 3. A device according to claim 1, wherein said duct (3; 24) isa substantially cylindrical body and comprises an open end forintroducing pressurised steam into said duct (3; 24) and a closed end onthe opposite side and wherein said at least one opening (5; 27) isprovided on the lateral surface of said duct, arranged so as to sendsteam into the liquid according to a predetermined trajectory.
 4. Adevice according to claim 1 or 3, wherein the opening or openings (5;27) in the duct (3; 24) are inclined downwards, so that steam flows outin a substantially radial and downward inclined direction.
 5. A deviceaccording to any claim 2 to 4, wherein said duct (3; 24) for introducingsteam is fastened onto the bottom of the container (1; 21) so that itsaxis is parallel with the axis of the container (1; 21), and it isprovided with a set of openings (5; 27) adapted to be covered by themilk when this is poured into 30 the container (1; 21).
 6. A deviceaccording to claim 3 or 4 or 5, wherein said duct (3; 24) is equippedwith means for the sealed connection with a steam-supplying spout, steamsupply causing steam to flow out from said openings (5; 27), and steamintroduction into the liquid creating the ideal conditions for frothingsame.
 7. A device according to clam 6, wherein said sealed connectionbetween said duct (3; 24) and said spout (11) is achieved through a jack(13), fitted into the upper end (15) of the duct (3; 24) with theinterposition of an O-ring (17).
 8. A device according to claim 5,wherein said duct (3; 24) from which steam flows into the milk to befrothed is removably fastened onto the bottom of the container (1; 21)by means of a threaded member (7), which is welded onto the bottom ofthe container (1; 21) and in which the lower end (9) of said duct (3;24) is screwed.
 9. A device according to claim 6, wherein saidsteam-supplying spout is the steam spout of an espresso coffee machine.10. An espresso coffee machine comp sing a steam-supplying spout;wherein the free end of said spout is equipped with a jack (13) adaptedto be fittingly coupled with a device made in accordance with any ofclaims 3 to
 9. 11. A device according to claim 1, wherein said container(1; 21) is a closed container associated with a first, a second and athird inlet ducts (24, 22, 25) for introducing pressurised steam intothe liquid for beating same and creating turbulence therein, introducingthe liquid to be processed into said chamber (1; 21), and introducingair necessary to frothing into the turbulent liquid, respectively, andwith a first and a second outlet ducts (32, 33) for discharging thefroth and the heated liquid, respectively.
 12. A device according toclaim 11, further comprising actuation means for automatically andsequentially starting the introduction of liquid, steam and, ifrequired, air, for controlling the amounts being introduced and fordischarging the froth and/or the hot liquid at the end of an operationcycle.
 13. A device according to claim 12, wherein said second inletduct (22) is associated with a pump (260 for taking dosed amounts ofsaid liquid from a vessel (23).
 14. A device according to claim 11 or12, wherein said first inlet duct (24) has, in an end section locatedinside the chamber (1; 21), a set of steam outlet nozzles (5; 27), whichare distributed along said lower section and are arranged so as to sendsteam into the liquid according to a predetermined trajectory.
 15. Adevice according to claim 14, wherein said first inlet duct (24) isconnected with a source of pressurised steam through a first way of atwo-way valve (29), of which a second way is connected with a secondsteam duct (30) intended to supply another utilisation device withpressurised steam.
 16. A device according to any of claims 11 to 15,wherein said inlet ducts penetrate into said chamber (1; 21) through achamber roof.
 17. A device according to claim 16, wherein the upperportion of said chamber (1; 21), including said roof, is removablymounted.
 18. A device according to any of claims 11 to 17, wherein saidthird inlet duct (25) and said outlet ducts (32, 33) are associated withrespective control valves (31, 35, 36) operated by said actuation meansat predetermined instants and for predetermined periods.
 19. A deviceaccording to any of claims 11 to 18, wherein said chamber (1; 21) isassociated with means for detecting and adjusting the temperature of theliquid within the chamber (1; 21), to allow supplying a liquid and/or afroth at a desired temperature, independent of the temperature of theliquid in the vessel (23).
 20. A device according to any of claims 11 to19, wherein said chamber (21) is associated with a further duct forintroducing pressurised steam, which is provided with nozzles of whichthe the cross-sections and the arrangement are such that they do notcreate turbulence in the liquid, and which is fed in place of said firstinlet duct (24), and in that sad actuation means are adapted to causeexecution of an operation cycle in which steam introduction takes placethrough said further inlet duct, and air introduction and frothdischarge are inhibited.
 21. A device according to claim 5 or 14,wherein the uppermost one of said openings (5; 27) is located a fewmillimeters below the level of the milk to be frothed.
 22. A deviceaccording to any preceding claim, wherein at least two said openings (5;27) are provided and they have a diameter of about 1 mm.
 23. An espressocoffee machine comprising means for producing stem and equipped with adevice for heating and frothing a liquid according to any of claims 11to 22.